Industrial hemp is legally defined in the United States as Cannabis which contains 0.3% or less total sample dry weight of Δ9-Tetrahydrocannabinal (THC). THC content is normally well above the 0.30% threshold in modern varieties of Cannabis. THC is one of an estimated 85 cannabinoids (a class of terpenoids) synthesized in Cannabis species (El-Alfy et al., 2010, “Antidepressant-like effect of delta-9-tetrahydrocannabinol and other cannabinoids isolated from Cannabis sativa L”, Pharmacology Biochemistry and Behavior 95 (4): 434-42).
Cannabinoids act on endogenous cannabinoid receptors located throughout the human body (Kreitzer and Stella, 2009, “The therapeutic potential of novel cannabinoid receptors”, Pharmacology & Therapeutics 122 (2): 83-96). These receptors are present in humans because the human body manufactures a similar class of cannabinoids known as the endocannabinoids (Pertwee et al., 2010, “International Union of Basic and Clinical Pharmacology. LXXIX. Cannabinoid Receptors and Their Ligands: Beyond CB1 and CB2”, Pharmacological Reviews 62 (4): 588-631).
The demand for the medicinal properties of cannabinoids derived from Cannabis is growing. Over the last 15 years, medicinal marijuana has gained similar regulatory ground as hemp. This is a reflection of consumer demand. In 2013, medical marijuana sales were estimated at 1.5 billion dollars. The medicinal effects of cannabinoids on human health continue to be validated as clinical research in this field expands and gains traction (Scott et al., 2014, “The Combination of Cannabidiol and Δ9-Tetrahydrocannabinol Enhances the Anticancer Effects of Radiation in an Orthotopic Murine Glioma Model”, Molecular Cancer Therapeutics 13 (12): 2955-2967). The ability to create this medicine without THC is highly desired by many patients and regulatory agencies.
Terpenes are a large class of volatile organic hydrocarbons. In plants, they function as hormones (e.g. abscisic acid), as photosynthetic pigments (e.g. carotenoids) and are involved in many other vital physiological processes. Secondary terpenoids (secondary metabolites) account for the majority of terpenoid molecular structural diversity. The secondary terpenoids play a major role in the plant's response to environmental factors such as such as pathogen and photooxidative stresses (Tholl, 2006, “Terpene synthases and the regulation, diversity and biological roles of terpene metabolism”, Current Opinion in Plant Biology 9 (3): 297-304). Apart from their functions in the plant, terpenes from hops (Humulus lupulus) such as myrcene and humulene serve as major aromatic and flavor compounds in beer. Cannabis synthesizes many terpenes including myrcene and humulene.
Cannabis normally reproduces under a dioecious system where male (staminate) and female (pistillate) flowers develop on separate plants. Monoecious plants (containing both male and female flowers) do exist. Female floral anatomy is characterized by pistils protruding from a calyx covered with resinous glandular trichomes. The glandular trichomes of the female flower are the primary site of cannabinoid synthesis. The female calyx contains ovaries and, therefore, is the site of seed development when fertilized by pollen produced by a male plant.
A vast majority of the Cannabis produced in the United States is done so by clonal propagation. Under this production scheme, meristems are cut from a selected plant and treated by various methods to induce rooting so that many, genetically identical progeny may be derived from the original. This is primarily done because breeding Cannabis seeds which consistently express a particular cannabinoid profile, often elevated for a particular cannabinoid (e.g. THC), is generally regarded as difficult. The simplicity of breeding varieties to be produced under a clonal reproduction system is quickly offset by the cost of clonal production, among other factors (Mckey et al., 2010, “The evolutionary ecology of clonally propagated domesticated plants”, New Phytologist 186 (2): 318-332). There is a need in the industry for industrial hemp varieties which are reliably low in THC when produced in diverse environmental conditions and which express elevated levels of certain other cannabinoids. The present invention provides a Cannabis variety that consistently and reproducibly has nearly zero THC (thus qualifying as industrial hemp) and elevated levels of CBD.
There are numerous steps in the development of any novel, desirable plant germplasm. Plant breeding preferably begins with the analysis and definition of problems and weaknesses of the current germplasm, the establishment of program goals, and the definition of specific breeding objectives. The next step is preferable selection of germplasm that possess the traits to meet the program goals. The goal is to combine in a single variety or hybrid an improved combination of desirable traits from the parental germplasm.